Bill Clinton has transformed from grandfatherly statesman to attack dog in a matter of days, aggressively going after Bernie Sanders on the campaign trail as the Vermont senator poses a rising threat to Democratic front-runner Hillary Clinton's bid.

“When you’re making a revolution, you can’t be too careful about the facts,” Clinton said at a Milford, N.H., event Sunday, a swipe at Sanders’ call for political upheaval.

He followed up Monday at an event at Manchester Community College,  accusing Sanders of demonizing anyone who disagrees with him.

“We can’t get in a place where we’re so mad that we demonize anyone who is against us, where we can’t have an honest discussion about health care, where anyone who is on the other side is part of a mystical ‘establishment,’” Clinton said. 

The tone marks an abrupt change from how the former president has conducted himself on the stump so far. Until this past weekend, his remarks largely were limited to talking about his wife’s biography, punctuated by tales of their dating life and how she has made everything she touches better. 

But with New Hampshire's primary just days away and Sanders holding a strong lead, the former president's role has changed.

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At Sunday’s event, Clinton painted Sanders as a foolhardy candidate whose proposals aren’t paid for and whose supporters include misogynists.

“People who have gone online to defend Hillary and explain why they supported her, have been subject to attacks that are literally too profane often, not to mention sexist, to repeat,” Clinton said.

Sanders has since disavowed such attacks against Clinton, saying “it's disgusting.”

On health care, Clinton accused Sanders of not having a plan that was properly accounted for.

“The New Hampshire I campaigned in really cared that you knew what you were doing, and how it was paid for,” Clinton said.

“For 20 years, Hillary’s opponent had a different plan, which he called single payer but it’s really 51 payer as states have to pay 14 percent of it,” Clinton said, before accusing Sanders of dropping the plan within 48 hours after he was questioned about it.

“Is [that] good for America? I don’t think so.” Clinton said.

Bill’s barbs have allowed the former secretary of state to take a softer stance against Sanders, telling supporters in Manchester that “Senator Sanders and I share a lot of the same goals,” before saying the difference between the two is the ability to get things done.

“I haven’t just talked, I haven’t just given speeches, I’ve passed legislation,” she said.

The former president’s latest barbs have echoes of 2008, when Clinton acted as attack dog against then-Sen. Barack Obama. Criticizing Obama’s claims on his Iraq war stance, Clinton called it the “biggest fairy tale” -- a put-down that was interpreted as a broad-brush slam on Obama’s quest to become the country’s first black president.

Later in South Carolina, Clinton got the name “hatchet man” for his attacks on Obama.